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Converting Bi fuel to gas only, PCM question

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  • Converting Bi fuel to gas only, PCM question

    So I am in the process of converting my truck back to gas only, I know that if I disconnect the gfi and all that fun stuff the truck will not start, so do I just get a used PCM from a gas truck and put in?

  • #2
    You can usually have the existing PCM re flashed. Is this a Ford with a compuvalve ? I am assuming this is to get your smog insp in UT.


    • #3
      I already passed this year in June, It's an old truck 220k I just want to able to work on it myself and have the space in the engine compartment to maneuver for spark plugs, vacuum leaks, all the typical maint. stuff and yes it is a 99 f250 light duty. So do I get it flashed to the VIN of my truck or a gas only one since mine is factory cng. I already had the tanks removed. Now I need new spark plugs, and fuel injectors correct?


      • #4
        If it's a 99 factory ford bi fuel, the alternate fuel stuff is on the dreaded gfi compuvalve. the gasoline injectors, spark plugs, etc should be the same as any gasoline only ford.. You shouldn't need to re flash anything. the system will think you are always out of alternate fuel and automatically go to gasoline. Does your state smog inspection require a bi fuel vehicle to be tested on both fuels ?

        EDIT: If it will not start on gasoline with the compuvalve disconnected, you are likely going to have to do some re-wiring if you want to remove it. Me, I would leave it and just remove all the tubing, and plug the holes in the intake manifold.
        Last edited by Lakewood90712; 11-15-2018, 12:44 PM.


        • #5
          I've got no idea how they do smog here in Utah, I passed in june and the system didn't work then either. I took it to a quicklube so they probably just passed it on gas. I have not fully disconnected it. I will try it and see if it starts. To others looking for information I emailed the GFI company and got this response. "Hi James,

          Unfortunately most of our present team was not actively involved on that project, so we don’t have the schematics or anything like that on-hand.
          However, if you wish to remove the GFI system, that should be fine as long as you conduct either of the following:

          There are 2 options that should help disconnect the CNG side and prevent any fault code / check engine lights from being set off.
          The first option is to unplug the red connector from the fuse module harness. This should cut the power to the CNG/Propane side and the internal routing of the relays should allow the engine to run just on gasoline and not search for CNG/Propane-side responses.
          If this does not work, then the second option is to reconnect the red connector, and disconnect the small grey connector. Take the mating connector which had been plugged in to this small grey connector, and jump it (you can use a pin to connect the terminals). This will also prevent the engine from connecting and searching for CNG/Propane-side signals.

          I believe if you just try to disconnect or rip out all the GFI system, the ECU is programmed to search for a response and will set off a fault code or check engine light if no response is received. Either of the 2 options listed above should prevent that."


          • #6
            Image sent by GFI employee
            Attached Files


            • #7
              Wow , you actually got a response from gfi. very good info. I am going to make this thread a sticky so others in the same situation will see it. Thanks for posting the details and image.